In return for the shares, Arris will receive $150 million cash from Comcast. More importantly, though, because of provision contained in its purchase agreement with Google, Arris' deal to sell shares to Comcast reduces Google's obligation to take shares from Arris in payment for Motorola Home, and at a 1-to-1 ratio. In lieu of half the shares it originally promised to Google, Arris will hand over an additional $150 million cash instead.

The upshot is that when all deals have been completed and Motorola Home moved to new ownership, Comcast and Google will each own 7.85% of Arris' shares outstanding, rather than Google with 15.7% and Comcast with none. Meanwhile, Arris ensures that two key partners have a vested interest in the success of its business.

Arris shares closed down 0.1% ahead of the news, at $15.34. Comcast shares closed up 1.2% at $38.92.